This study introduces a novel approach to radar-based hand gesture recognition (HGR), addressing the challenges of energy efficiency and reliability by employing real-time gesture recognition at the frame level. Our solution bypasses the computationally expensive preprocessing steps, such as 2D fast Fourier transforms (FFTs), traditionally employed for range-Doppler information generation. Instead, we capitalize on time-domain radar data and harness the energy-efficient capabilities of spiking neural networks (SNNs) models, recognized for their sparsity and spikes-based communication, thus optimizing the overall energy efficiency of our proposed solution. Experimental results affirm the effectiveness of our approach, showcasing significant classification accuracy on the test dataset, with peak performance achieving a mean accuracy of 99.75%. To further validate the reliability of our solution, individuals who have not participated in the dataset collection conduct real-time live testing, demonstrating the consistency of our theoretical findings. Real-time inference reveals a substantial degree of spikes sparsity, ranging from 75% to 97%, depending on the presence or absence of a performed gesture. By eliminating the computational burden of preprocessing steps and leveraging the power of (SNNs), our solution presents a promising alternative that enhances the performance and usability of radar-based (HGR) systems.

Metamaterial lenses are appealing thin alternatives to conventional dielectric lenses. In this contribution we describe their design and application in two exemplary 77 GHz automotive radar sensors operating in monostatic and bistatic modes. The frontends are built around commercially available MMICs and small feed antennas are used in coordination with the six-layer printed circuit board-based realizations of metamaterial lenses. The design follows the principles of dielectric lenses, while the required local phase shift is obtained from a set of metasurface bandpasses. Their design uses a novel interpolation procedure to extract layout parameters for a given phase shift. Despite the small structural sizes due to the high frequency, the fabricated frequency-selective surfaces show very good performance in the required frequency range. Verification measurements were conducted on single bandpasses as well as on metamaterial lenses mounted on the radar frontend. The results agree very well with the simulation and confirm the applicability of thin lenses operating at mm-wave frequencies for automotive radar applications.

This work introduces a method for plasma state supervision, based on a frequency-modulated continuous wave radar sensor and a suitable signal evaluation enabling a continuous supervision method for the plasma state. Highly precise phase evaluation of the signal allows us to detect and visualize smallest changes in the plasma state. Assuming the plasma to act like a frequency-dependent dielectric material, the propagation of the electromagnetic wave depends on the plasma state and hence, also the measured phase. Broadband measurements are carried out at center frequencies of 80 and 140 GHz in a low-pressure plasma. The radar-based setup can be used for a very flexible application, capable for spatially resolved measurements in the plasma bulk. At the same time, the high measurement rate allows for quasi real-time monitoring, so that transient processes in the plasma are recorded. Due to the simple setup, this approach is most suitable for industrial applications to improve process control. The chosen different frequencies will show a change in the influence of the plasma on the electromagnetic wave demonstrating the advantages of multi-frequency approaches in future applications.

In this paper, we present several dielectric waveguide (DWG) setups that enable the transition between radar front ends and antennas in challenging, industrial environments. Apart from good propagation behavior, DWG provide a nearly dispersion free transmission over large distances. Furthermore, they can be used as an electrical insulator in places with critical creep distances, in high temperature environments, and for applications with limited installation space. Fundamentals concerning the ideal propagation mode and adequate waveguide–fiber transitions are presented. Results of electromagnetic simulations as well as measurements on manufactured DWG are discussed in detail. The presented excellent propagation behavior proves the effectiveness of the proposed setup.

A highly integrated silicon platform (Hi-Mission) for high frequency applications is introduced. This platform utilizes heterogeneous Multi-Chip Module-Deposited (MCM-D) technology with integrated passive devices together with silicon and GaAs Monolithic Microwave Integrated Circuit (MMIC) technology developed for the automotive Ultra Wide Band (UWB) radar (short-range radar) frequency band from 77 to 81 GHz. Developments are described in the area of MCM-D process development, MMIC, integrated phased array antenna, module design, and assembly process development. The demonstrator is composed of two test vehicles designed for conducted and radiated measurements, respectively. Test results are presented at the component and module level.